Electrical systems transmit electric current through electrical conductors in order to perform many tasks. Many applications of electrical systems may require sensing of the magnitude of electric current flowing through one or more electrical conductors. Some electrical systems sense the electric current in an electrical conductor with a magnetoresistive sensor that senses the magnetic flux produced by the electric current and produces an output signal related to the magnitude of the magnetic flux and, thus, the magnitude of the electric current. Unfortunately, a magnetoresistive sensor may be able to accurately sense only a limited range of magnetic flux intensity. As a result, many electrical systems that employ a magnetoresistive sensor for current sensing are able to accurately sense only a limited range of electric current using the magnetoresistive sensor.
U.S. Pat. No. 4,525,668 to Lienhard et al. (“the '668 patent”) shows a current-sensing method that includes sensing magnetic flux from both an unknown current and a control current with a magnetoresistive sensor, while using the control current to maintain the total magnetic flux sensed by the magnetoresistive sensor substantially equal to zero. The '668 patent discloses an electrical system that includes a first electrical conductor carrying the unknown current adjacent the magnetoresistive sensor. A second electrical conductor disposed adjacent the magnetoresistive sensor carries the controlled current. The electrical system of the '668 patent further includes an operational amplifier connected between the magnetoresistive sensor and the second electrical conductor. The operational amplifier receives the output signal of the magnetoresistive sensor and controls the magnitude of the control current in the second electrical conductor in such a manner that magnetic flux from the control current substantially cancels magnetic flux from the unknown current at the magnetoresistive sensor. The electrical system of the '668 patent includes additional analog components that use the control current to generate a signal indicative of the magnitude of the unknown current.
Although the system of the '668 patent includes provisions for sensing electric current with a magnetoresistive sensor while maintaining the total magnetic flux sensed by the magnetoresistive sensor substantially equal to zero, certain disadvantages persist. For example, the electrical system of the '668 patent may be undesirably expensive because of the component costs associated with separately providing the magnetoresistive sensor and the second electrical conductor. Additionally, precisely positioning the second electrical conductor with respect to the magnetoresistive sensor so as to ensure proper operation of the electrical system may be difficult and expensive. Furthermore, the analog components of the electrical system of the '668 patent may indicate the magnitude of the unknown electric current with relatively low resolution.
The electrical systems and methods of the present disclosure solve one or more of the problems set forth above.